Technical Field
The invention relates to a method and an apparatus for mechanically recovering flesh from slaughtered fish with opened abdominal cavity, particularly from fish species having pin bones extending from the spine into the fish flesh, for example salmon (salmo solar) or white fish.
State of the Art
It is known for recovering fillets from fish to cut the ventral and dorsal spokes or bones of the fish up to the vertebrae of the spine both from above and also from below by means of two rotating circular blade pairs spaced apart, to cut free the fillets in the region of the abdominal cavity by means of rib incisions from the lateral vertebral processes and ribs or flank bones, and to separate them completely from the bone structure by separating the meat strip from the tail root to behind the abdominal cavity. A filleting machine for carrying out this method, in which a conveyor that is fitted at intervals with sliding saddles for receiving the slaughtered fish conveys the fish tail-first through a processing area, is disclosed in DE 29 12 982 C2. To carry out an effective filleting process, in which pin-bone-free fillets should be recovered from fish of the type described above, a method is proposed in DE 22 48 536 A in which, after carrying out the dorsal incisions and scraping of the flesh from the vertebral processes, the flesh is scraped off closely above the pin bones and is then separated from the ribs and if necessary the ventral spokes.
A further apparatus for manufacturing pin-bone-free fish fillets is disclosed in DE 35 18 960 CI. During the filleting process, circular knives are used to make lateral incisions essentially perpendicular to the plane of symmetry of the fish above the pin bones up to the dorsal spokes as a result of which, in continuing the filleting process, the boneless fillets and the ventral flaps arise separately. Finally, an apparatus for recovering pin-bone-free fish fillets is disclosed in DE 36 32 561 C2 in which during filleting two rotating circular knives spaced apart from each other make two incisions above and below the pin bones running approximately perpendicular to the plane of symmetry of the fish up to the ribs or the lateral vertebral processes. A burin knife which fills the intermediate space between the pin bone knives separates out the meat strips containing the pin bones. In this way, fillets are obtained that are free of pin bones and other bones but to which the ventral flap adheres. This is undesirable during the recovery of pin-bone-free fish fillets.
In contrast to the known methods for recovering pin-bone-free fish fillets in which the pin bones are separated from the spine and are then removed in a separate work operation, DE 101 16 248 A proposes a method for filleting slaughtered fish with opened abdominal cavity in which the pin bones are left on the spine and in a separate work step are drawn out of the fish flesh while exerting relative deformation forces between the pin bones and the flesh regions surrounding them. During the process, the pin bones are pushed out of their originally upright position, essentially perpendicular to the spine, towards the spine until they assume a position approximately parallel to it. Due to this deformation and associated load on the pin bones, there is a risk that the pin bones will be detached from the spine and will break away from it while being drawn out of the fish flesh. As a result, the pin bones remain completely or partially in the fish flesh which means a reduction in the quality of the fish fillets obtained.
According to effective fish processing technologies, the object of the invention is therefore to supplement and further develop the known filleting and deboning methods in such a manner that, as a result of the processing procedure, a pin-bone-free fish fillet emerges without any fish bone remnants in the fish flesh and without damage to the fish flesh.
This object is achieved by a method having the features indicated in claim 1 and by an apparatus having the features indicated in claim 9. Preferred embodiments emerge from the associated dependent claims in addition to the following description and the accompanying figures.